The present invention relates to a device for injecting a material in the form of a suspension, and in particular a grout, into a cavity.
More precisely, the invention relates to a device making it possible to improve the effectiveness of injection by means of a hollow tube type system into a hole made in a structure in order to treat it. The device is particularly well adapted to treating vaults, i.e. when injection needs to be directed upwards.
As shown in FIG. 1, it can be necessary to make a hole 10 in a structure 12 in order to inject grout for treating the structure. With known techniques, grout is injected by means of a tube 14 whose end penetrates into the hole 10, a sealing plug 16 being made, for example, around the tube in order to seal the hole 10 at least temporarily during injection. That system is entirely effective providing the air initially contained in the hole and the cavities within its walls can escape while injection is taking place. Otherwise, when that is not the case, the air becomes compressed inside the hole and injection comes to an end before the hole has been completely filled because of the increase in pressure.
To resolve that problem, proposals have been made to associate the grout injection tube 14 with a vent hose enabling the air held captive in the hole to escape. However, the presence of two tubes passing through the sealing plug 16 makes sealing very difficult or even impossible to obtain. Under such circumstances, water can flow freely between the zones where the two tubes pass through and marks of dampness appear at the plug 16.
An object of the present invention is to provide apparatus for injecting material in the form of a suspension, and in particular a grout, enabling a vent to be put into place simultaneously, but without presenting the above-mentioned drawbacks.
To achieve this object, the invention provides a device for injecting material in the form of a suspension into a cavity, the device comprising:
an injection tube for injecting said material, the tube having a first end for coupling and a second end that is open to allow said material to escape into said cavity;
a coupling having a cylindrical portion provided with an axial bore having a first end for coupling to the first end of said tube and a second end, said coupling also having a radial stub;
a material feed pipe connected to said stub;
a vent hose engaged in said tube and in said coupling, said vent hose having a first end projecting from the second end of the tube to collect the air contained in said cavity, and a second end that is open to allow the air to escape and that projects from the second end of the coupling; and
a sealing piece for sealing the second end of said coupling to the outside wall of said hose.
It will be understood that the vent hose passes through the sealing zone at the entrance to the cavity inside the grout injection tube. There is thus only one pipe passage to be sealed. This is made possible by the fact that a sealing piece is fitted to provide sealing between the grout injection tube and the portion of the vent hose that goes to the outside. Nevertheless, the vent function is performed at least as effectively as in the configuration where the vent tube is outside the grout injection tube.
In a first embodiment, the sealing piece has a first end provided with a thread for co-operating with a thread provided at the second end of the coupling, and a second end suitable for taking up a first position in which it clamps in sealed manner against the outside wall of said vent hose and a second position in which it is spaced apart from the wall of said hose.
Also preferably, at rest, said second end of the sealing piece is in its first or clamping position, and the sealing piece further comprises a control member for bringing said second end into its second position.
It will be understood that because of the removable nature of the sealing piece, it is possible to separate the grout injection tube or more precisely its coupling with the vent hose after grout has been injected into the wall.